1. Field of the Invention
The present invention relates to a slide locking mechanism for a seat.
2. Description of the Related Art
Heretofore, there has been known a slide locking mechanism for a seat, such as an automobile seat. For example, the conventional slide locking mechanism has a locking member held by an upper rail which is fixed to a seat in such a manner that a longitudinal direction of the upper rail is oriented along a frontward-rearward direction of an automobile body. Further, the slide locking mechanism has a plurality of latch portions having the same configurations, the latch portions are provided in a bottom wall of a lower rail fixed to the automobile body, and arranged in one line along the longitudinal direction. Each of the latch portions has a hole formed to allow the locking member to be releasably inserted thereinto. The locking member is formed such that a width thereof in the longitudinal direction is equal to an opening width of each of the holes of the latch portions in the longitudinal direction.
In the slide locking mechanism, when a seated person moves the seat to a target position in the frontward-rearward direction, the locking member is inserted into the hole of one of the latch portions which is located at a position (appropriate position) corresponding to the target position, according to a biasing force of biasing means, to establish a locked state where the inserted locking member is latched by the corresponding latch portion, so that the upper rail and the lower rail are locked together. This allows the seat to be fixed with respect to the automobile body.
However, when the seated person moves the seat to a target position in the frontward-rearward direction, the slide locking mechanism is likely to fall into an undesirable situation where the locking member is not aligned with any one of the latch portions, so that the locking member is brought into contact with a portion between adjacent ones of the latch portions and precluded from being inserted into the hole of any one of the latch portions. In this situation, for example, if the seat is pushed in the frontward or rearward direction by the seated person, the locking member is liable to be quickly moved in the frontward or rearward direction before it is inserted into the latch portion adjacent to the appropriate position, so that the locking member passes over the appropriate position in the bottom wall of the lower rail.
In this case, as the opening width of each of the holes of the latch portions is gradually increased relative to the width of the locking member, the locking member becomes more easily insertable into the hole of one of the latch portions. However, this approach leads to the occurrence of a play (free gap in the longitudinal direction) between the inserted locking member and the corresponding latch portion, which causes a wobbling movement of the seat in the locked state to preclude the seat from being fixed.
Therefore, a locking mechanism has been proposed which is designed to allow a locking member to be easily inserted into a hole of one of a plurality of latch portions, while preventing the occurrence of a play between the inserted locking member and an corresponding one of the latch portions, as disclosed, for example, in JP 10-500647A. In the locking mechanism disclosed in the JP 10-500647A, the locking member is comprised of a plurality of locking bolts each formed to be insertable into the hole (detent opening) of each of the latch portions, wherein the locking bolts are arranged in one line in a frontward-rearward direction of a vehicle at regular intervals. Each of the locking bolts is provided to be rotatable about an axis thereof by rotation means. When two of the locking bolts are inserted into respective ones of two of the latch portions, each of the locking bolts is rotated about the axis by the rotation means. According to the rotation, one of the two locking bolts inserted into respective ones of the two latch portions is brought into contact with a front inner wall region of one of the two latch portions, and the other locking bolt is brought into contact with a rear inner wall region of the other latch portion. Thus, in the locked state, a play in both the frontward and rearward directions is eliminated to prevent a wobbling movement of a seat (see FIG. 6 in the JP 10-500647A).
However, in the locking mechanism disclosed in the JP 10-500647A, it is necessary to provide the rotation means to each of the locking bolts in order to rotate the locking bolt about the axis, which leads to structural complexity and an increase in cost.
Moreover, in the locking mechanism disclosed in the JP 10-500647A, when an upper rail is urged to be moved in the frontward or rearward direction relative to a lower rail in the locked state, a force applied to the upper rail at the time is imposed on one of the two locking bolts inserted into respective ones of the holes of the two latch portions. Thus, the force is concentrically imposed on the inserted locking bolt, and the front or rear inner wall region of an corresponding one of the two latch portions. Therefore, in order to prevent fracture of the inserted locking bolt and damage in the front or rear inner wall region of the corresponding latch portion in such a situation, strength of each of the locking bolts and the lower rail has to be increased, which causes a problem of an increase in cost.